A wind turbine blade design is optimized for a given standard design environment including mean wind speed, turbulence, and other factors. Once the blade mold is created, the outer geometry and aerodynamic response of the blade is fixed. Blade design is a balance between power production and turbine loads, and must meet International Electrotechnical Commission requirements for a specific wind class. Molds are expensive and blade designs are standardized and are used for many wind turbines.